(i) Field to which invention relates
The invention is with respect to a continuous flow heater with a compound heating structure made up of bodies of material with a high thermal conductivity and each having a heat input face and a fluidway running through it for fluid to be continuously heated, the bodies being so positioned that their heat input faces are turned towards each other and the fluidways are parallel to each other, with at least one heating element placed between the heat input faces, and with a casing forcing the bodies together with the heating element therebetween. More specially, though not in all cases so, the invention is with respect to a continuous flow heater on these lines used as an evaporator or broiler in beverage making machines such as coffee making machines or the like. Continuous flow heaters of this sort may furthermore be used for many other purposes in the most different walks of life and for different heating powers.
(ii) The prior art
In the case of an earlier design of continuous flow heater of the sort noted the bodies take the form of sectors of cylinders put together for forming a complete cylindrical heating structure and pushed together with a certain force by a cylindrical casing, made for example of flexible sheet metal for tightly forcing the parts together. The heating elements are in this case placed between two radial faces (turned towards each other) on each one cylinder sector and the next one. The fluidways, which are parallel to each other and to the axis of the cylinder, for the fluid as for example water to be heated, are joined with each other without the cylinder sectors by pieces of flexible pipe or connection covers having connection fluidways (see German Offenlegungsschrift specification No. 2,804,749).
This known design of continuous flow heater of the sort noted has generally gone down well in the trade because of the thermal efficiency and the simple process for making it, this being true more specially in the case of higher electrical power levels. On the other hand for designing apparatus with a generally low electrical power and which is generally produced on a mass scale, so that a low price is more specially to be desired, the prior art design noted has not been able to be produced with the low material and labor costs desired in industry. Furthermore, designing for different heating levels generally makes it necessary for the heating structure to be made up of a different number of cylinder sectors with different sector angles so that a great number of different parts have to be kept on hand and warehoused.